/*
*********************************************************************************************************
*                                                uC/OS-II
*                                          The Real-Time Kernel
*                                  MUTUAL EXCLUSION SEMAPHORE MANAGEMENT
*
*                          (c) Copyright 1992-2006, Jean J. Labrosse, Weston, FL
*                                           All Rights Reserved
*
* File    : OS_MUTEX.C
* By      : Jean J. Labrosse
* Version : V2.84
*********************************************************************************************************
*/

#ifndef  OS_MASTER_FILE
#include <ucos_ii.h>
#endif


#if OS_MUTEX_EN > 0
/*
*********************************************************************************************************
*                                            LOCAL CONSTANTS
*********************************************************************************************************
*/

#define  OS_MUTEX_KEEP_LOWER_8   0x00FFu
#define  OS_MUTEX_KEEP_UPPER_8   0xFF00u

#define  OS_MUTEX_AVAILABLE      0x00FFu

/*
*********************************************************************************************************
*                                            LOCAL CONSTANTS
*********************************************************************************************************
*/

static  void  OSMutex_RdyAtPrio(OS_TCB *ptcb, INT8U prio);

/*$PAGE*/

/*
*********************************************************************************************************
*                                   ACCEPT MUTUAL EXCLUSION SEMAPHORE
*
* Description: This  function checks the mutual exclusion semaphore to see if a resource is available.
*              Unlike OSMutexPend(), OSMutexAccept() does not suspend the calling task if the resource is
*              not available or the event did not occur.
*
* Arguments  : pevent     is a pointer to the event control block
*
*              err        is a pointer to an error code which will be returned to your application:
*                            OS_NO_ERR          if the call was successful.
*                            OS_ERR_EVENT_TYPE  if 'pevent' is not a pointer to a mutex
*                            OS_ERR_PEVENT_NULL 'pevent' is a NULL pointer
*                            OS_ERR_PEND_ISR     if you called this function from an ISR
*                            OS_ERR_PIP_LOWER    If the priority of the task that owns the Mutex is
*                                                HIGHER (i.e. a lower number) than the PIP.  This error
*                                                indicates that you did not set the PIP higher (lower
*                                                number) than ALL the tasks that compete for the Mutex.
*                                                Unfortunately, this is something that could not be
*                                                detected when the Mutex is created because we don't know
*                                                what tasks will be using the Mutex.
*
* Returns    : == 1       if the resource is available, the mutual exclusion semaphore is acquired
*              == 0       a) if the resource is not available
*                         b) you didn't pass a pointer to a mutual exclusion semaphore
*                         c) you called this function from an ISR
*
* Warning(s) : This function CANNOT be called from an ISR because mutual exclusion semaphores are
*              intended to be used by tasks only.
*********************************************************************************************************
*/

#if OS_MUTEX_ACCEPT_EN > 0
INT8U  OSMutexAccept (OS_EVENT *pevent, INT8U *err)
{
        INT8U      pip;                                    /* Priority Inheritance Priority (PIP)          */
#if OS_CRITICAL_METHOD == 3                            /* Allocate storage for CPU status register     */
        OS_CPU_SR  cpu_sr = 0;
#endif
#if OS_ARG_CHK_EN > 0

        if (err == (INT8U *)0)                             /* Validate 'err'                               */
        {
                return (0);
        }

        if (pevent == (OS_EVENT *)0)                       /* Validate 'pevent'                            */
        {
                *err = OS_ERR_PEVENT_NULL;
                return (0);
        }

#endif

        if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX)    /* Validate event block type                    */
        {
                *err = OS_ERR_EVENT_TYPE;
                return (0);
        }

        if (OSIntNesting > 0)                              /* Make sure it's not called from an ISR        */
        {
                *err = OS_ERR_PEND_ISR;
                return (0);
        }

        OS_ENTER_CRITICAL();                               /* Get value (0 or 1) of Mutex                  */
        pip = (INT8U)(pevent->OSEventCnt >> 8);            /* Get PIP from mutex                           */

        if ((pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8) == OS_MUTEX_AVAILABLE)
        {
                pevent->OSEventCnt &= OS_MUTEX_KEEP_UPPER_8;   /*      Mask off LSByte (Acquire Mutex)         */
                pevent->OSEventCnt |= OSTCBCur->OSTCBPrio;     /*      Save current task priority in LSByte    */
                pevent->OSEventPtr  = (void *)OSTCBCur;        /*      Link TCB of task owning Mutex           */

                if (OSTCBCur->OSTCBPrio <= pip)                /*      PIP 'must' have a SMALLER prio ...      */
                {
                        OS_EXIT_CRITICAL();                        /*      ... than current task!                  */
                        *err  = OS_ERR_PIP_LOWER;
                }
                else
                {
                        OS_EXIT_CRITICAL();
                        *err  = OS_NO_ERR;
                }

                return (1);
        }

        OS_EXIT_CRITICAL();
        *err = OS_NO_ERR;
        return (0);
}
#endif

/*$PAGE*/
/*
*********************************************************************************************************
*                                  CREATE A MUTUAL EXCLUSION SEMAPHORE
*
* Description: This function creates a mutual exclusion semaphore.
*
* Arguments  : prio          is the priority to use when accessing the mutual exclusion semaphore.  In
*                            other words, when the semaphore is acquired and a higher priority task
*                            attempts to obtain the semaphore then the priority of the task owning the
*                            semaphore is raised to this priority.  It is assumed that you will specify
*                            a priority that is LOWER in value than ANY of the tasks competing for the
*                            mutex.
*
*              err           is a pointer to an error code which will be returned to your application:
*                               OS_NO_ERR           if the call was successful.
*                               OS_ERR_CREATE_ISR   if you attempted to create a MUTEX from an ISR
*                               OS_PRIO_EXIST       if a task at the priority inheritance priority
*                                                   already exist.
*                               OS_ERR_PEVENT_NULL  No more event control blocks available.
*                               OS_PRIO_INVALID     if the priority you specify is higher that the
*                                                   maximum allowed (i.e. > OS_LOWEST_PRIO)
*
* Returns    : != (void *)0  is a pointer to the event control clock (OS_EVENT) associated with the
*                            created mutex.
*              == (void *)0  if an error is detected.
*
* Note(s)    : 1) The LEAST significant 8 bits of '.OSEventCnt' are used to hold the priority number
*                 of the task owning the mutex or 0xFF if no task owns the mutex.
*
*              2) The MOST  significant 8 bits of '.OSEventCnt' are used to hold the priority number
*                 to use to reduce priority inversion.
*********************************************************************************************************
*/

OS_EVENT  *OSMutexCreate (INT8U prio, INT8U *err)
{
        OS_EVENT  *pevent;
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
        OS_CPU_SR  cpu_sr = 0;
#endif
#if OS_ARG_CHK_EN > 0

        if (err == (INT8U *)0)                                 /* Validate 'err'                           */
        {
                return ((OS_EVENT *)0);
        }

        if (prio >= OS_LOWEST_PRIO)                            /* Validate PIP                             */
        {
                *err = OS_PRIO_INVALID;
                return ((OS_EVENT *)0);
        }

#endif

        if (OSIntNesting > 0)                                  /* See if called from ISR ...               */
        {
                *err = OS_ERR_CREATE_ISR;                          /* ... can't CREATE mutex from an ISR       */
                return ((OS_EVENT *)0);
        }

        OS_ENTER_CRITICAL();

        if (OSTCBPrioTbl[prio] != (OS_TCB *)0)                 /* Mutex priority must not already exist    */
        {
                OS_EXIT_CRITICAL();                                /* Task already exist at priority ...       */
                *err = OS_PRIO_EXIST;                              /* ... inheritance priority                 */
                return ((OS_EVENT *)0);
        }

        OSTCBPrioTbl[prio] = (OS_TCB *)1;                      /* Reserve the table entry                  */
        pevent             = OSEventFreeList;                  /* Get next free event control block        */

        if (pevent == (OS_EVENT *)0)                           /* See if an ECB was available              */
        {
                OSTCBPrioTbl[prio] = (OS_TCB *)0;                  /* No, Release the table entry              */
                OS_EXIT_CRITICAL();
                *err               = OS_ERR_PEVENT_NULL;           /* No more event control blocks             */
                return (pevent);
        }

        OSEventFreeList        = (OS_EVENT *)OSEventFreeList->OSEventPtr;   /* Adjust the free list        */
        OS_EXIT_CRITICAL();
        pevent->OSEventType    = OS_EVENT_TYPE_MUTEX;
        pevent->OSEventCnt     = (INT16U)((INT16U)prio << 8) | OS_MUTEX_AVAILABLE; /* Resource is avail.   */
        pevent->OSEventPtr     = (void *)0;                                 /* No task owning the mutex    */
#if OS_EVENT_NAME_SIZE > 1
        pevent->OSEventName[0] = '?';
        pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
        OS_EventWaitListInit(pevent);
        *err                   = OS_NO_ERR;
        return (pevent);
}

/*$PAGE*/
/*
*********************************************************************************************************
*                                          DELETE A MUTEX
*
* Description: This function deletes a mutual exclusion semaphore and readies all tasks pending on the it.
*
* Arguments  : pevent        is a pointer to the event control block associated with the desired mutex.
*
*              opt           determines delete options as follows:
*                            opt == OS_DEL_NO_PEND   Delete mutex ONLY if no task pending
*                            opt == OS_DEL_ALWAYS    Deletes the mutex even if tasks are waiting.
*                                                    In this case, all the tasks pending will be readied.
*
*              err           is a pointer to an error code that can contain one of the following values:
*                            OS_NO_ERR               The call was successful and the mutex was deleted
*                            OS_ERR_DEL_ISR          If you attempted to delete the MUTEX from an ISR
*                            OS_ERR_INVALID_OPT      An invalid option was specified
*                            OS_ERR_TASK_WAITING     One or more tasks were waiting on the mutex
*                            OS_ERR_EVENT_TYPE       If you didn't pass a pointer to a mutex
*                            OS_ERR_PEVENT_NULL      If 'pevent' is a NULL pointer.
*
* Returns    : pevent        upon error
*              (OS_EVENT *)0 if the mutex was successfully deleted.
*
* Note(s)    : 1) This function must be used with care.  Tasks that would normally expect the presence of
*                 the mutex MUST check the return code of OSMutexPend().
*
*              2) This call can potentially disable interrupts for a long time.  The interrupt disable
*                 time is directly proportional to the number of tasks waiting on the mutex.
*
*              3) Because ALL tasks pending on the mutex will be readied, you MUST be careful because the
*                 resource(s) will no longer be guarded by the mutex.
*
*              4) IMPORTANT: In the 'OS_DEL_ALWAYS' case, we assume that the owner of the Mutex (if there
*                            is one) is ready-to-run and is thus NOT pending on another kernel object or
*                            has delayed itself.  In other words, if a task owns the mutex being deleted,
*                            that task will be made ready-to-run at its original priority.
*********************************************************************************************************
*/

#if OS_MUTEX_DEL_EN
OS_EVENT  *OSMutexDel (OS_EVENT *pevent, INT8U opt, INT8U *err)
{
        BOOLEAN    tasks_waiting;
        OS_EVENT  *pevent_return;
        INT8U      pip;                                        /* Priority inheritance priority            */
        INT8U      prio;
        OS_TCB    *ptcb;
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
        OS_CPU_SR  cpu_sr = 0;
#endif
#if OS_ARG_CHK_EN > 0

        if (err == (INT8U *)0)                                 /* Validate 'err'                           */
        {
                return ((OS_EVENT *)0);
        }

        if (pevent == (OS_EVENT *)0)                           /* Validate 'pevent'                        */
        {
                *err = OS_ERR_PEVENT_NULL;
                return ((OS_EVENT *)0);
        }

#endif

        if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX)        /* Validate event block type                */
        {
                *err = OS_ERR_EVENT_TYPE;
                return (pevent);
        }

        if (OSIntNesting > 0)                                  /* See if called from ISR ...               */
        {
                *err = OS_ERR_DEL_ISR;                             /* ... can't DELETE from an ISR             */
                return (pevent);
        }

        OS_ENTER_CRITICAL();

        if (pevent->OSEventGrp != 0)                           /* See if any tasks waiting on mutex        */
        {
                tasks_waiting = OS_TRUE;                           /* Yes                                      */
        }
        else
        {
                tasks_waiting = OS_FALSE;                          /* No                                       */
        }

        switch (opt)
        {
                case OS_DEL_NO_PEND:                               /* DELETE MUTEX ONLY IF NO TASK WAITING --- */
                        if (tasks_waiting == OS_FALSE)
                        {
#if OS_EVENT_NAME_SIZE > 1
                                pevent->OSEventName[0] = '?';             /* Unknown name                             */
                                pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
                                pip                 = (INT8U)(pevent->OSEventCnt >> 8);
                                OSTCBPrioTbl[pip]   = (OS_TCB *)0;        /* Free up the PIP                          */
                                pevent->OSEventType = OS_EVENT_TYPE_UNUSED;
                                pevent->OSEventPtr  = OSEventFreeList;    /* Return Event Control Block to free list  */
                                pevent->OSEventCnt  = 0;
                                OSEventFreeList     = pevent;
                                OS_EXIT_CRITICAL();
                                *err                = OS_NO_ERR;
                                pevent_return       = (OS_EVENT *)0;      /* Mutex has been deleted                   */
                        }
                        else
                        {
                                OS_EXIT_CRITICAL();
                                *err                = OS_ERR_TASK_WAITING;
                                pevent_return       = pevent;
                        }

                        break;

                case OS_DEL_ALWAYS:                                /* ALWAYS DELETE THE MUTEX ---------------- */
                        pip  = (INT8U)(pevent->OSEventCnt >> 8);                     /* Get PIP of mutex          */
                        prio = (INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8);  /* Get owner's original prio */
                        ptcb = (OS_TCB *)pevent->OSEventPtr;

                        if (ptcb != (OS_TCB *)0)                      /* See if any task owns the mutex           */
                        {
                                if (ptcb->OSTCBPrio == pip)               /* See if original prio was changed         */
                                {
                                        OSMutex_RdyAtPrio(ptcb, prio);        /* Yes, Restore the task's original prio    */
                                }
                        }

                        while (pevent->OSEventGrp != 0)               /* Ready ALL tasks waiting for mutex        */
                        {
                                (void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_MUTEX);
                        }

#if OS_EVENT_NAME_SIZE > 1
                        pevent->OSEventName[0] = '?';                 /* Unknown name                             */
                        pevent->OSEventName[1] = OS_ASCII_NUL;
#endif
                        pip                 = (INT8U)(pevent->OSEventCnt >> 8);
                        OSTCBPrioTbl[pip]   = (OS_TCB *)0;            /* Free up the PIP                          */
                        pevent->OSEventType = OS_EVENT_TYPE_UNUSED;
                        pevent->OSEventPtr  = OSEventFreeList;        /* Return Event Control Block to free list  */
                        pevent->OSEventCnt  = 0;
                        OSEventFreeList     = pevent;                 /* Get next free event control block        */
                        OS_EXIT_CRITICAL();

                        if (tasks_waiting == OS_TRUE)                 /* Reschedule only if task(s) were waiting  */
                        {
                                OS_Sched();                               /* Find highest priority task ready to run  */
                        }

                        *err          = OS_NO_ERR;
                        pevent_return = (OS_EVENT *)0;                /* Mutex has been deleted                   */
                        break;

                default:
                        OS_EXIT_CRITICAL();
                        *err          = OS_ERR_INVALID_OPT;
                        pevent_return = pevent;
                        break;
        }

        return (pevent_return);
}
#endif

/*$PAGE*/
/*
*********************************************************************************************************
*                                  PEND ON MUTUAL EXCLUSION SEMAPHORE
*
* Description: This function waits for a mutual exclusion semaphore.
*
* Arguments  : pevent        is a pointer to the event control block associated with the desired
*                            mutex.
*
*              timeout       is an optional timeout period (in clock ticks).  If non-zero, your task will
*                            wait for the resource up to the amount of time specified by this argument.
*                            If you specify 0, however, your task will wait forever at the specified
*                            mutex or, until the resource becomes available.
*
*              err           is a pointer to where an error message will be deposited.  Possible error
*                            messages are:
*                               OS_NO_ERR          The call was successful and your task owns the mutex
*                               OS_TIMEOUT         The mutex was not available within the specified time.
*                               OS_ERR_EVENT_TYPE  If you didn't pass a pointer to a mutex
*                               OS_ERR_PEVENT_NULL 'pevent' is a NULL pointer
*                               OS_ERR_PEND_ISR    If you called this function from an ISR and the result
*                                                  would lead to a suspension.
*                               OS_ERR_PIP_LOWER   If the priority of the task that owns the Mutex is
*                                                  HIGHER (i.e. a lower number) than the PIP.  This error
*                                                  indicates that you did not set the PIP higher (lower
*                                                  number) than ALL the tasks that compete for the Mutex.
*                                                  Unfortunately, this is something that could not be
*                                                  detected when the Mutex is created because we don't know
*                                                  what tasks will be using the Mutex.
*
* Returns    : none
*
* Note(s)    : 1) The task that owns the Mutex MUST NOT pend on any other event while it owns the mutex.
*
*              2) You MUST NOT change the priority of the task that owns the mutex
*********************************************************************************************************
*/
void  OSMutexPend (OS_EVENT *pevent, INT16U timeout, INT8U *err)
{
        INT8U      pip;                                        /* Priority Inheritance Priority (PIP)      */
        INT8U      mprio;                                      /* Mutex owner priority                     */
        BOOLEAN    rdy;                                        /* Flag indicating task was ready           */
        OS_TCB    *ptcb;
        OS_EVENT  *pevent2;
        INT8U      y;
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
        OS_CPU_SR  cpu_sr = 0;
#endif
#if OS_ARG_CHK_EN > 0

        if (err == (INT8U *)0)                                 /* Validate 'err'                           */
        {
                return;
        }

        if (pevent == (OS_EVENT *)0)                           /* Validate 'pevent'                        */
        {
                *err = OS_ERR_PEVENT_NULL;
                return;
        }

#endif

        if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX)        /* Validate event block type                */
        {
                *err = OS_ERR_EVENT_TYPE;
                return;
        }

        if (OSIntNesting > 0)                                  /* See if called from ISR ...               */
        {
                *err = OS_ERR_PEND_ISR;                            /* ... can't PEND from an ISR               */
                return;
        }

        if (OSLockNesting > 0)                                 /* See if called with scheduler locked ...  */
        {
                *err = OS_ERR_PEND_LOCKED;                         /* ... can't PEND when locked               */
                return;
        }

        OS_ENTER_CRITICAL();
        pip = (INT8U)(pevent->OSEventCnt >> 8);                /* Get PIP from mutex                       */

        /* Is Mutex available?                      */
        if ((INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8) == OS_MUTEX_AVAILABLE)
        {
                pevent->OSEventCnt &= OS_MUTEX_KEEP_UPPER_8;       /* Yes, Acquire the resource                */
                pevent->OSEventCnt |= OSTCBCur->OSTCBPrio;         /*      Save priority of owning task        */
                pevent->OSEventPtr  = (void *)OSTCBCur;            /*      Point to owning task's OS_TCB       */

                if (OSTCBCur->OSTCBPrio <= pip)                    /*      PIP 'must' have a SMALLER prio ...  */
                {
                        OS_EXIT_CRITICAL();                            /*      ... than current task!              */
                        *err  = OS_ERR_PIP_LOWER;
                }
                else
                {
                        OS_EXIT_CRITICAL();
                        *err  = OS_NO_ERR;
                }

                return;
        }

        mprio = (INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8);  /* No, Get priority of mutex owner   */
        ptcb  = (OS_TCB *)(pevent->OSEventPtr);                       /*     Point to TCB of mutex owner   */

        if (ptcb->OSTCBPrio > pip)                                    /*     Need to promote prio of owner?*/
        {
                if (mprio > OSTCBCur->OSTCBPrio)
                {
                        y = ptcb->OSTCBY;

                        if ((OSRdyTbl[y] & ptcb->OSTCBBitX) != 0)             /*     See if mutex owner is ready   */
                        {
                                OSRdyTbl[y] &= ~ptcb->OSTCBBitX;                  /*     Yes, Remove owner from Rdy ...*/

                                if (OSRdyTbl[y] == 0)                             /*          ... list at current prio */
                                {
                                        OSRdyGrp &= ~ptcb->OSTCBBitY;
                                }

                                rdy = OS_TRUE;
                        }
                        else
                        {
                                pevent2 = ptcb->OSTCBEventPtr;

                                if (pevent2 != (OS_EVENT *)0)                     /* Remove from event wait list       */
                                {
                                        if ((pevent2->OSEventTbl[ptcb->OSTCBY] &= ~ptcb->OSTCBBitX) == 0)
                                        {
                                                pevent2->OSEventGrp &= ~ptcb->OSTCBBitY;
                                        }
                                }

                                rdy = OS_FALSE;                            /* No                                       */
                        }

                        ptcb->OSTCBPrio = pip;                         /* Change owner task prio to PIP            */
#if OS_LOWEST_PRIO <= 63
                        ptcb->OSTCBY    = (INT8U)( ptcb->OSTCBPrio >> 3);
                        ptcb->OSTCBX    = (INT8U)( ptcb->OSTCBPrio & 0x07);
                        ptcb->OSTCBBitY = (INT8U)(1 << ptcb->OSTCBY);
                        ptcb->OSTCBBitX = (INT8U)(1 << ptcb->OSTCBX);
#else
                        ptcb->OSTCBY    = (INT8U)((ptcb->OSTCBPrio >> 4) & 0xFF);
                        ptcb->OSTCBX    = (INT8U)( ptcb->OSTCBPrio & 0x0F);
                        ptcb->OSTCBBitY = (INT16U)(1 << ptcb->OSTCBY);
                        ptcb->OSTCBBitX = (INT16U)(1 << ptcb->OSTCBX);
#endif

                        if (rdy == OS_TRUE)                            /* If task was ready at owner's priority ...*/
                        {
                                OSRdyGrp               |= ptcb->OSTCBBitY; /* ... make it ready at new priority.       */
                                OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
                        }
                        else
                        {
                                pevent2 = ptcb->OSTCBEventPtr;

                                if (pevent2 != (OS_EVENT *)0)              /* Remove from event wait list              */
                                {
                                        pevent2->OSEventGrp               |= ptcb->OSTCBBitY;
                                        pevent2->OSEventTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
                                }
                        }

                        OSTCBPrioTbl[pip] = ptcb;
                }
        }

        OSTCBCur->OSTCBStat   |= OS_STAT_MUTEX;           /* Mutex not available, pend current task        */
        OSTCBCur->OSTCBPendTO  = OS_FALSE;
        OSTCBCur->OSTCBDly     = timeout;                 /* Store timeout in current task's TCB           */
        OS_EventTaskWait(pevent);                         /* Suspend task until event or timeout occurs    */
        OS_EXIT_CRITICAL();
        OS_Sched();                                       /* Find next highest priority task ready         */
        OS_ENTER_CRITICAL();

        if (OSTCBCur->OSTCBPendTO == OS_TRUE)             /* See if we timed out during the pend           */
        {
                OS_EventTO(pevent);
                OS_EXIT_CRITICAL();
                *err = OS_TIMEOUT;                            /* Indicate that we didn't get mutex within TO   */
                return;
        }

        OSTCBCur->OSTCBEventPtr = (OS_EVENT *)0;
        OS_EXIT_CRITICAL();
        *err = OS_NO_ERR;
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                  POST TO A MUTUAL EXCLUSION SEMAPHORE
*
* Description: This function signals a mutual exclusion semaphore
*
* Arguments  : pevent              is a pointer to the event control block associated with the desired
*                                  mutex.
*
* Returns    : OS_NO_ERR               The call was successful and the mutex was signaled.
*              OS_ERR_EVENT_TYPE       If you didn't pass a pointer to a mutex
*              OS_ERR_PEVENT_NULL      'pevent' is a NULL pointer
*              OS_ERR_POST_ISR         Attempted to post from an ISR (not valid for MUTEXes)
*              OS_ERR_NOT_MUTEX_OWNER  The task that did the post is NOT the owner of the MUTEX.
*              OS_ERR_PIP_LOWER        If the priority of the new task that owns the Mutex is
*                                      HIGHER (i.e. a lower number) than the PIP.  This error
*                                      indicates that you did not set the PIP higher (lower
*                                      number) than ALL the tasks that compete for the Mutex.
*                                      Unfortunately, this is something that could not be
*                                      detected when the Mutex is created because we don't know
*                                      what tasks will be using the Mutex.
*********************************************************************************************************
*/

INT8U  OSMutexPost (OS_EVENT *pevent)
{
        INT8U      pip;                                   /* Priority inheritance priority                 */
        INT8U      prio;
#if OS_CRITICAL_METHOD == 3                           /* Allocate storage for CPU status register      */
        OS_CPU_SR  cpu_sr = 0;
#endif

        if (OSIntNesting > 0)                             /* See if called from ISR ...                    */
        {
                return (OS_ERR_POST_ISR);                     /* ... can't POST mutex from an ISR              */
        }

#if OS_ARG_CHK_EN > 0

        if (pevent == (OS_EVENT *)0)                      /* Validate 'pevent'                             */
        {
                return (OS_ERR_PEVENT_NULL);
        }

#endif

        if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX)   /* Validate event block type                     */
        {
                return (OS_ERR_EVENT_TYPE);
        }

        OS_ENTER_CRITICAL();
        pip  = (INT8U)(pevent->OSEventCnt >> 8);          /* Get priority inheritance priority of mutex    */
        prio = (INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8);  /* Get owner's original priority      */

        if (OSTCBCur != (OS_TCB *)pevent->OSEventPtr)     /* See if posting task owns the MUTEX            */
        {
                OS_EXIT_CRITICAL();
                return (OS_ERR_NOT_MUTEX_OWNER);
        }

        if (OSTCBCur->OSTCBPrio == pip)                   /* Did we have to raise current task's priority? */
        {
                OSMutex_RdyAtPrio(OSTCBCur, prio);            /* Restore the task's original priority          */
        }

        OSTCBPrioTbl[pip] = (OS_TCB *)1;                  /* Reserve table entry                           */

        if (pevent->OSEventGrp != 0)                      /* Any task waiting for the mutex?               */
        {
                /* Yes, Make HPT waiting for mutex ready         */
                prio                = OS_EventTaskRdy(pevent, (void *)0, OS_STAT_MUTEX);
                pevent->OSEventCnt &= OS_MUTEX_KEEP_UPPER_8;  /*      Save priority of mutex's new owner       */
                pevent->OSEventCnt |= prio;
                pevent->OSEventPtr  = OSTCBPrioTbl[prio];     /*      Link to new mutex owner's OS_TCB         */

                if (prio <= pip)                              /*      PIP 'must' have a SMALLER prio ...       */
                {
                        OS_EXIT_CRITICAL();                       /*      ... than current task!                   */
                        OS_Sched();                               /*      Find highest priority task ready to run  */
                        return (OS_ERR_PIP_LOWER);
                }
                else
                {
                        OS_EXIT_CRITICAL();
                        OS_Sched();                               /*      Find highest priority task ready to run  */
                        return (OS_NO_ERR);
                }
        }

        pevent->OSEventCnt |= OS_MUTEX_AVAILABLE;         /* No,  Mutex is now available                   */
        pevent->OSEventPtr  = (void *)0;
        OS_EXIT_CRITICAL();
        return (OS_NO_ERR);
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                     QUERY A MUTUAL EXCLUSION SEMAPHORE
*
* Description: This function obtains information about a mutex
*
* Arguments  : pevent          is a pointer to the event control block associated with the desired mutex
*
*              p_mutex_data    is a pointer to a structure that will contain information about the mutex
*
* Returns    : OS_NO_ERR            The call was successful and the message was sent
*              OS_ERR_QUERY_ISR     If you called this function from an ISR
*              OS_ERR_PEVENT_NULL   If 'pevent'       is a NULL pointer
*              OS_ERR_PDATA_NULL    If 'p_mutex_data' is a NULL pointer
*              OS_ERR_EVENT_TYPE    If you are attempting to obtain data from a non mutex.
*********************************************************************************************************
*/

#if OS_MUTEX_QUERY_EN > 0
INT8U  OSMutexQuery (OS_EVENT *pevent, OS_MUTEX_DATA *p_mutex_data)
{
        INT8U      i;
#if OS_LOWEST_PRIO <= 63
        INT8U     *psrc;
        INT8U     *pdest;
#else
        INT16U    *psrc;
        INT16U    *pdest;
#endif
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */
        OS_CPU_SR  cpu_sr = 0;
#endif

        if (OSIntNesting > 0)                                  /* See if called from ISR ...               */
        {
                return (OS_ERR_QUERY_ISR);                         /* ... can't QUERY mutex from an ISR        */
        }

#if OS_ARG_CHK_EN > 0

        if (pevent == (OS_EVENT *)0)                           /* Validate 'pevent'                        */
        {
                return (OS_ERR_PEVENT_NULL);
        }

        if (p_mutex_data == (OS_MUTEX_DATA *)0)                /* Validate 'p_mutex_data'                  */
        {
                return (OS_ERR_PDATA_NULL);
        }

#endif

        if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX)        /* Validate event block type                */
        {
                return (OS_ERR_EVENT_TYPE);
        }

        OS_ENTER_CRITICAL();
        p_mutex_data->OSMutexPIP  = (INT8U)(pevent->OSEventCnt >> 8);
        p_mutex_data->OSOwnerPrio = (INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8);

        if (p_mutex_data->OSOwnerPrio == 0xFF)
        {
                p_mutex_data->OSValue = 1;
        }
        else
        {
                p_mutex_data->OSValue = 0;
        }

        p_mutex_data->OSEventGrp  = pevent->OSEventGrp;        /* Copy wait list                           */
        psrc                      = &pevent->OSEventTbl[0];
        pdest                     = &p_mutex_data->OSEventTbl[0];

        for (i = 0; i < OS_EVENT_TBL_SIZE; i++)
        {
                *pdest++ = *psrc++;
        }

        OS_EXIT_CRITICAL();
        return (OS_NO_ERR);
}
#endif                                                     /* OS_MUTEX_QUERY_EN                        */

/*$PAGE*/
/*
*********************************************************************************************************
*                                RESTORE A TASK BACK TO ITS ORIGINAL PRIORITY
*
* Description: This function makes a task ready at the specified priority
*
* Arguments  : ptcb            is a pointer to OS_TCB of the task to make ready
*
*              prio            is the desired priority
*
* Returns    : none
*********************************************************************************************************
*/

static  void  OSMutex_RdyAtPrio (OS_TCB *ptcb, INT8U prio)
{
        INT8U   y;
        y            =  ptcb->OSTCBY;                          /* Remove owner from ready list at 'pip'    */
        OSRdyTbl[y] &= ~ptcb->OSTCBBitX;

        if (OSRdyTbl[y] == 0)
        {
                OSRdyGrp &= ~ptcb->OSTCBBitY;
        }

        ptcb->OSTCBPrio         = prio;
#if OS_LOWEST_PRIO <= 63
        ptcb->OSTCBY            = (INT8U)((prio >> 3) & 0x07);
        ptcb->OSTCBX            = (INT8U) (prio & 0x07);
        ptcb->OSTCBBitY         = (INT8U)(1 << ptcb->OSTCBY);
        ptcb->OSTCBBitX         = (INT8U)(1 << ptcb->OSTCBX);
#else
        ptcb->OSTCBY            = (INT8U)((prio >> 4) & 0x0F);
        ptcb->OSTCBX            = (INT8U) (prio & 0x0F);
        ptcb->OSTCBBitY         = (INT16U)(1 << ptcb->OSTCBY);
        ptcb->OSTCBBitX         = (INT16U)(1 << ptcb->OSTCBX);
#endif
        OSRdyGrp               |= ptcb->OSTCBBitY;             /* Make task ready at original priority     */
        OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
        OSTCBPrioTbl[prio]      = ptcb;
}


#endif                                                     /* OS_MUTEX_EN                              */
